The two brother generally wear . . . . . . clothes.

The two brothers....

Using 'each other' is more applicable when talking about only two people (or things).
Using ‘one another’ is more relevant when there are more than two people (or things).

Answer should be "each other"

There is very little difference in meaning between each other and one another. One another is fairly formal, and many people do not use it at all. Some people prefer to use each other when they are talking about two people or things, and one another when they are talking about more than two.

(Each other) for two
One another) for more than two